Control of circular dichroism in ion yield of 3-methyl cyclopentanone with femtosecond laser pulses

Circular dichroism (CD) in ion yield in the gas phase is a promising chiral recognition technique. Combining it with broadband ultrafast laser pulses allows us to examine the possibility of coherent control. We used shaped femtosecond laser pulses to control the CD in ion yield of 3-methylcyclopentanone observed from a 1 + 1 + 1 resonance-enhanced multiphoton ionisation around 309 nm. The duration of the pulses is increased via their spectral width or a frequency chirp, and a pulse pair with adjustable delay is employed to study the effect on the CD in ion yield. Furthermore, we used strongly chirped pulses of different central wavelengths to control the observed anisotropy. A clear enhancement of the anisotropy can be achieved, and possible mechanisms are discussed.